Sulfur containing synthetic lubricating compositions



United States Patent SULFUR CONTAININ G SYNTHETIC LUBRI- CATING COMPOSITION S Alfred H. Matuszak, Westfield, and Harold R; Ready, Roselle Park, N. J.,. assignors to E'sso Research and Engineering Company, a corporation of Delaware No Drawing; Application March 10, 1954, Serial No. 415,424 g 8 Claims. (Cl. 252-48.6)

This invention relates tosynthetio lubricating compositions. Particularly the invention relates to-synthetic lubricating compositionshaving outstanding'lubricating properties at both-high andlowtemperatures and which have the advantage ofleaving substantially no combustion chamber deposits in the cylinders of reciprocating engines. More particularly, the invention relates to synthetic lubricating compositions having outstandingextreme pressure resisting characteristics in addition to their general lubrieating properties which comprise thioorthoformates and mercaptoles of ca to C20 organic compounds. The materials of thisinvention correspond to the formula wherein R' is either hydrogenor an alkyl group containing from 8 to 20 carbon'atoms, R is either an alkyl group containing from 8 to 20 carbon atoms or the group XR", X is oxygen or sulfur with at least one X being sulfur and R" is an alkyl radical containing from 8 to 20 carbon atoms.

Especially preferred and contemplated in the preferred embodiment of this invention are compounds of the formula wherein X, Y 'and Z areoxygen or sulfur, with at least one being sulfur, and wherein RR and R" are alkyl groups containingfrom 8--t-o 20 carbon atoms, preferably 10-18 carbon atoms, at least one alkyl group being of branched chain configuration.

In recent efforts .to obtain superior lubr'icatingcompositions which have unusual and specific properties, there have been developed entirely new synthetic materials with lubricating properties. In general these new synthetic lubricants are characterized by viscosity properties that are outstanding at both'low and high temperatures, especially when compared to mineral. oils. These outstanding low and high temperature properties are especially desirable for use in equipment designed to operate over a great temperature differential, suchas jet engines. for aircraft use, combustion engines for aircraft and the like. It has been found that mineral lubricating oils are generally undesirable for the lubrication of these engines because of their high and low temperature viscosity limitations.

It has also been found that synthetic lubricants may be desirable for the lubrication of' standard automotive engines. In addition to the versatility of their viscosities, the use of some types of the synthetic lubricants investigated have been'found: to result in very low rates of combustion chamber deposit formation, particularly when "ice used for long periods oftime. Low rates of formation of combustion chamber deposits result in increased power factor from fuel, less increase in the octane requirement of the engine, less pre-ignition tendency, and a general overall improvement in engine operation. These new lubricants may also serve to reduce or remove combustion chamber deposits from an engine already loaded with such deposits.

For use in reciprocating engines, particularly as a lubricant forautomotive engines, a lubricating composition must meet several requirements. Inorder to form an effective lubricating film and to maintain that film at low and high temperatures it must have certain viscosity characteristics. At low temperatures, the lubricant must be sufficiently labile to flow through'the circulatory system of the equipment andallowmove'ment' of lubricated surfaces Without an undue power requirement. A lubricant having an ASTM. pour point below about" 35 F. has suflicient low temperaturelability to make it satisfactory in these respects for general use. At high temperatures, a lubricant must have sufficient body or thickness to furnish and maintain a satisfactory lubricating film. It has been found that a lubricant that is satisfactory in this respect will have a viscosity at 210 F. of between about 2 to 60 centistokes, i. e., about 32 to 280 Saybolt seconds, Universal. To prevent undue lubricant loss, due to volatility andgeneral molecular disintegration and to insure against explosion haz'ards at higher temperatures sometimesencountered, a lubricating composition should have a flash point in excess of about 300 F. These requisites are inherent in the term lubricating compositions as used in this specificatiom andthe materials of this invention are limited to those within these operable'rang'es. The preferred materials, ascontemplated herein and as described in the preferred embodiment hereof,'will have an ASTM pour point below about 15 F., a flash point above about 375 F.', and will have a viscosity within the range of 2.6 to 1'3 centistokes, i. e., 35 to 70 Saybolt seconds, Universal, at 210 F.

In general it has been found'that the above listedproperties are a function both of molecular structure and of molecular weight. This fact makes it possible, within certain limits, toprepare compositions having similar low and high temperature properties in a variety of ways and also enables the manufacturer totailor a composition to, fit a certain set of specifications within rather general limits.

The materials in accordance with the instant invention may be quite simply prepared by reacting a mercaptan or a mixture of mercaptans and alcohols with a simple formate in the presence of a catalyst. This reaction proceeds in accordance with the following equation:

3RXH+ (R'O)3CH (RX) 3CH+3R'OH Q X being oxygen or sulfur.

The instant invention will be more clearly explained by reference to the following illustrative example:

Example 1.Preparation of di-lauryl. mono-C13 Oxo dithioorthoformate lauryl mercaptan (405 g., 2 in.) C13 Oxo alcohol prepared from a C12 olefin polymer fraction predominating in tetra-propylene (245 g., l rn.+45 g. excess), triethylorthoformate (148 g., 1 m.), and toluenesulfonic acid (3.1 g.) were brought to a reflux under a 15 plate column with a variable takeoff head. After 3 hours, 162 cc. of ethyl alcohol had been removed. The kettle temperature reached a maximum temperature of 225 C. After filtering off the catalyst and pumping stones the material was stripped to C. overhead (kettle at 227 C.) at 0.6 mm. to give '500 g. of product having the following properties:

Kin. vis.: 210, cs 5.78

100, cs 29.33 V. I 145 Pour point, "P 50 Flash point, F 430 Fire point, "F 470 Neut.No 0.15 Percent sulfur 10.56

1 (Theory is 10.42.)

The data set out above shows the desirable lubricating characteristics of this illustrative material.

The load-carrying characteristics of the material of Example 1 above were determined as follows:

A blend of 5.0 wt. percent of the material of Example 1 in di-Z-ethylhexyl sebacate was prepared. The evaluation of the load carrying properties of the blend was made in the well known SAE E. P. lubricant tester in Which the machine bearings are lubricated by the oil undergoing the test. The machine is started under a 50# load on the bearings and is run for 2 minutes. Following the break-in period, an additional 50# load is added manually every 10 seconds until scuffing oc curs. An average of two or more runs is normally sufficient to characterize the lubricant.

In the table below, the results of the load carrying tests on the blend of the material of Example 1 are set out with various other synthetic oils of current interest.

TABLE I Load carrying ability of synthetic lubricants SAE-SOD Test Load, Lbs.

Lubricant Material of Example 1 1, (100 DI-Z-ethylhexyl sebacate 500 95.0 wt. percent Di-2-ethylhexyl sebacate+5.0 wt.

percent of material of Example 1 Complex Ester (of 5 below) 95.0 percent Di-2-ethylhexyl sebacate+5.0 percent of complex ester (2-ethylhexanol-sebacic acid poly ethylene glycol-sebacic acid-2-ethylhexanol) It is to be seen that the load carrying characteristics Temperatures=100250 C.

Time of reaction=1 to hours.

Catalysts operable=NaHSO4, toluene sulfonic acid,

ZnClz, H2804, etc.

The final product may be filtered to remove catalyst, washed with an alkaline solution to remove excess acidic materials, washed with Water and then stripped to a pot temperature of about 200 to 250 C. and about 0.1 to 5.0 mm./Hg pressure.

The mercaptoles of this invention may be prepared in a similar manner by reacting (1) orthothioformates with ketones or (2) mercaptans with ketones. Mixed orthoesters i. e. X=0 and S can then be obtained by reacting the ortho trithioester with an alcohol (or mercaptan) having a boiling point higher than the mercaptan or alcohol to be evolved. Acidic catalysts are preferred. Reaction temperature will vary between 100 and 250 C.

Of the various CaC2o alcohols and mercaptans operable in the concept of this invention, the following may be mentioned.

Amyl alcohol Amyl mercaptan Z-ethyl-l-hexanol 2-ethyl-1-hexyl mercaptan Octanol Octyl mercaptan Iso-octanol 2-octyl alcohol Isononyl alcohol Decyl alcohol. Lauryl alcohol Tetradecyl alcohol Pentadecyl alcohol Octadecyl alcohol Allyl alcohol Crotyl alcohol Oleyl alcohol Cs-zo Oxo alcohol Iso-octyl mercaptan 2-octy1 mercaptan. Isononyl mercaptan Decyl mercaptan Lauryl mercaptan Tetradecyl mercaptan Octadecyl mercaptan Allyl mercaptan Crotyl mercaptan Oleyl mercaptan Ca-ao Oxo mercaptan Particularly desirable compounds for use in this invention are those highly branched chain aliphatic alcohols prepared by the 0x0 synthesis and their corresponding mercaptans.

The 0x0 synthesis may be described as being the catalytic reaction of an olefin with carbon monoxide and hydrogen. The reaction occurs at temperatures in the order of 300-400 F., at pressures in the range of about 1000 to 3000 p. s. i., in the presence of suitable catalyst, ordinarily a heavy metal carbonyl such as cobalt carbonyl. The resulting aldehyde is subsequently hydrogenated to a primary alcohol. This process is described in U. S. Patent No. 2,327,066 issued to Roelen in 1943.

It has been found that particularly desirable alcohols for the formation of the materials of this invention can be prepared by the application of the 0x0 synthesis to polymers and copolymers of Ca and C4 monoolefins. These monoolefins are readily available in petroleum refinery streams and processes for their conversion to liquid copolymers have been worked out by the art. One such process, known as U. 0. P. polymerization, consists of passing the olefin-containing stream in liquid phase in contact with an acid catalyst comprising phosphoric acid impregnated on kieselguhr. Other acidic catalysts, such as phosphoric acid or copper phosphate impregnated on silica gel, sulfuric acid, Friedel-Crafts catalysts, activated clays, silica-alumina, copper pyrophosphate, etc., may be used. Suitable conditions when employing phosphoric acid catalysts of the U. 0. P. type are temperatures of 300 F. to 500? F., pressures from 250 to 5,000 p. s. i. and feed stocks comprising refinery streams containing propylene and mixed butylenes. Suitable feed stocks, for example, may contain from 15 to 60 mol percentpropylenes, from 0.5 to 15 mol percent butylenes, and from 0.1 to 10 mol percent isobutylene, the remaining being saturated hydrocarbons. Other suitable feed stocks are the dimer and trimer of isobutylene.

The preferred Oxo alcohols employed in forming the materials of this invention are those having from .8 to 20 carbon atoms derived from olefin copolymers having from 7 to 19 carbon atoms. Especially preferred are those Oxo alcohols having from 10 to 18 carbon atoms. In preparing these Oxo alcohols the desired olefin fraction is segre- "gated from the crude olefin polymer product by fractionation and then subjected to the 0x0 process as described above.

T It is also within the concept of this invention to utilize corresponding alkylene oxide derivatives of the above materials, for example, glycol monoethers and glycol-thic- .ethers, in preparing "the orthoformates ofuthis invention. Glycol monoesters, vhydroxy acid'monoesters, glycolformals and their corresponding mercaptor and alkylene oxide derivitives may also be used. Glycols :andipolyhydric compounds including mercapto-types may also be used togive higher viscosityrmaterials which would presumably have dumbbell type structures, in that the glycol would connect two or more thioorthoesters or mercaptoles.

It is also within-the concept of this invention to com-= pletely react the formates with themencaptan or alcohol to form ortho-compounds of thestructure Thioortho- 'lhioorthoformate of formate of Example Example 1 1+4% Polymethacrylate Viscosity, es. F.:

210 5. 78 7. 51 100 29. 3 36.66 85 Viscosity Index 145 154 The materials of this invention are useful as plasticizers, solubilizers, grease bases, insecticides, weed killers, rust preventives, heating oil additives, solvents, dewaxing aids, detergents, and as raw materials for many other industrial applications, such as household detergents, fumigants, etc. These new synthetic lubricating oils may be admixed with other lubricating oils, naturally occurring or synthetic, either as concentrates or as finished blends. They are compatible and may be blended with the well known lubricant addition agents such as viscosity index improvers, pour point depressors, detergents, rust inhibitors, load carrying agents, antioxidants and the like.

The orthoformates and mercaptoles as described herein may serve as the lubricant base for grease compositions. These synthetic lubricants may be thickened to stable grease structures with conventional grease forming soaps such as lithium soaps of high molecular weight substantially saturated fatty acid, the n-acyl p-amino phenols, silica gels, treated bentonites and the like. Oxidation inhibitors, rust inhibitors, tackiness agents and other grease addition agents may be added to the ortho esters of this invention. The soap complexes known to the art made by using low molecular weight acid salts may also be used in preparing these grease compositions. If desired the materials of this invention may be blended with mineral oil or other synthetic lubricants such as simple bis-formals, complex esters, monoesters, diesters, triesters, tetraesters, phosphates, siloxanes, silicates, phosphonates and the like, and a grease composition which incorporates the desirable characteristics of the blends may be prepared by conventional techniques.

To summarize briefly, the instant invention relates to new compositions of matter which have outstanding utility as synthetic lubricating compositions, having lubricating characteristics at both high and low temperatures and having, in addition, outstanding load carrying properties. The materials contemplated herewith may be broadly described as being the thioorthoformates and mercaptoles of organic. compoundshaving'from. 8. to 20carbon atoms,

preferably 10%18 carbon zatoms. .These new synthetic lubricants may be described by the following general formula $1 R-O(XR)1 wherein-R is either hydrogen or an alkyl group containing -from'8 :to 20 carbon atoms, R'is either an alkyl group-containing from 8' to 20 carbon atoms or the group -XR", X is oxygen or sulfur, and R is an alkyl radical containing from' 8 to 20 carbon atoms. At least one 'ofthe' radicals 'R,v R, or'R mustbe of branched chain -configuration, and at least one'X must be sulfur. The

total number of carbon atoms in the molecule must be between 20 and preferably between about 25 and 100.

The compounds that are especially preferred and that are considered to comprise the preferred embodiment of this invention are those materials having a kinematic viscosity within the range of from 2 to 60 centistokes at 210 R, an ASTM pour point of at least as low as 35 F., and a flash point of at least 300 F. The preferred compounds are described by the formula wherein X, Y and Z are either oxygen or sulfur, at least one being sulfur, and wherein R, R and R" are alkyl groups containing from 8 to 20 carbon atoms, at least one alkyl group being of branched chain configuration.

What is claimed is: l. A synthetic lubricant of the formula wherein X, Y and Z are selected from the group consisting of oxygen and sulfur, at least one being sulfur, and wherein R, R, R" are alkyl radicals containing from 10 to 18 carbon atoms, at least one radical being of branched chain configuration, said composition containing from 20 to 130 carbon atoms per molecule and having a kinematic viscosity at 210 F. of between 2 and 60 centistokes, an ASTM pour point below about 35 F., and a flash point above about 300 F.

2. A lubricant according to claim 1 wherein R and R are straight chain alkyl groups containing from 10 to 18 carbon atoms each and wherein R" is a branched chain alkyl group containing from 10 to 18 carbon atoms.

3. A lubricant according to claim 1 wherein R and R are straight chain alkyl groups containing about 12 carbon atoms, and wherein R is an alkyl group of branched chain configuration containing about 13 carbon atoms.

4. A lubricant according to claim 1 wherein at least one of the group of X, Y and Z, is a sulfur atom.

5. A lubricant according to claim 1 wherein R and R are straight chained alkyl groups containing about 12 carbon atoms each, wherein R" is a branched chain alkyl group containing about 13 carbon atoms, and wherein X, and Y are sulfur and wherein Z is oxygen.

6. A synthetic lubricant which comprises a major amount of di-Z-ethyl hexyl sebacate having blended therein a minor, but extreme pressure resistance improving, amount of the lubricant of claim 1.

7. A synthetic lubricant which comprises a major amount of a di-2-ethyl hexyl sebacate containing combined therein a minor, but extreme pressure resistance improving, amount of a di-lauryl-mono-Cm Oxo thio ortho formate, said C13 Oxo radical being derived from an alcohol prepared by subjecting a C12 olefin to the action of carbon monoxide and hydrogen in the presence of a cobalt catalyst at a temperature of about 300-400 F. and a pressure of about 1000 to 3000 p. s. i,

wherein X, Y and Z are selected from the group consisting of oxygen and sulfur, at least one being sulfur, and wherein R, R, R" are alkyl radicals containing from 1 0 to 18 carbon atoms, at least one radical being of branched chain configuration, said composition containing from 20 to 130 carbon atoms per molecule and having a kinematic viscosity at 210 F. of between 2 and 60 centistokes, an

-ASTM pour point below about 35 F., and a flash point above about 300 F., and a minor but viscosity index improving amount ofan oil-soluble polymer of a Ca' C1o acrylate ester.

References' Cited in the file of this patent UNITED STATES PATENTS 2,322,093 Moran et al June 15, 1943 2,389,153 Kendall Nov. 20, 1945 2,552,510 Barker et al May 15, 1951 2,566,157 Barker et a1 Aug. 28, 1951 

1. A SYNTHETIC LUBRICANT OF THE FORMULA 